Outputs (71)

Black holes in multimetric gravity. II. Hairy solutions and linear stability of the non- and partially proportional branches (2025)
Journal Article
Wood, K., Saffin, P. M., & Avgoustidis, A. (2025). Black holes in multimetric gravity. II. Hairy solutions and linear stability of the non- and partially proportional branches. Physical Review D, 111(2), Article 024057. https://doi.org/10.1103/PhysRevD.111.024057

Owing to our work in part I of this series of papers, it is understood that the analytically known black hole solutions in the theory of ghost-free multimetric gravity can be split into three distinct classes and that one of these classes—the proport... Read More about Black holes in multimetric gravity. II. Hairy solutions and linear stability of the non- and partially proportional branches.

de Sitter vacua in O(d,d) invariant cosmology (2024)
Journal Article
Liu, Y., Padilla, A., Saffin, P. M., & Smith, R. G. C. (2024). de Sitter vacua in O(d,d) invariant cosmology. Physical Review D, 110(6), Article 063522. https://doi.org/10.1103/physrevd.110.063522

We perform a thorough analysis of de Sitter solutions in O⁡(𝑑,𝑑) invariant cosmologies. Starting with a homogeneous and isotropic framework we examine conditions for the existence of such solutions to the vacuum field equations, nonperturbative in 𝛼′... Read More about de Sitter vacua in O(d,d) invariant cosmology.

Black holes in multimetric gravity (2024)
Journal Article
Wood, K., Saffin, P. M., & Avgoustidis, A. (2024). Black holes in multimetric gravity. Physical Review D, 109(12), Article 124006. https://doi.org/10.1103/physrevd.109.124006

We construct a wide class of black hole solutions to the general theory of ghost-free multimetric gravity in arbitrary spacetime dimension, extending and generalizing the known results in four-dimensional dRGT massive gravity and bigravity. The solut... Read More about Black holes in multimetric gravity.

Ringdowns for black holes with scalar hair: The large mass case (2024)
Journal Article
D’Addario, G., Padilla, A., Saffin, P. M., Sotiriou, T. P., & Spiers, A. (2024). Ringdowns for black holes with scalar hair: The large mass case. Physical Review D, 109(8), Article 084046. https://doi.org/10.1103/physrevd.109.084046

Deviations from general relativity can alter the quasinormal mode (QNM) ringdown of perturbed black holes. It is known that a shift-symmetric (hence massless) scalar can only introduce black hole hair if it couples to the Gauss-Bonnet invariant, in w... Read More about Ringdowns for black holes with scalar hair: The large mass case.

Quantum corrected Q-ball dynamics (2024)
Journal Article
Xie, Q.-X., Saffin, P. M., Tranberg, A., & Zhou, S.-Y. (2024). Quantum corrected Q-ball dynamics. Journal of High Energy Physics, 2024(1), Article 165. https://doi.org/10.1007/jhep01%282024%29165

The physics of individual Q-balls and interactions between multiple Q-balls are well-studied in classical numerical simulations. Interesting properties and phenomena have been discovered, involving stability, forces, collisions and swapping of charge... Read More about Quantum corrected Q-ball dynamics.

Q-Ball Superradiance (2023)
Journal Article
Saffin, P. M., Xie, Q.-X., & Zhou, S.-Y. (2023). Q-Ball Superradiance. Physical Review Letters, 131(11), Article 111601. https://doi.org/10.1103/physrevlett.131.111601

Q-balls are nontopological solitons that coherently rotate in field space. We show that these coherent rotations can induce superradiance for scattering waves, thanks to the fact that the scattering involves two coupled modes. Despite the conservatio... Read More about Q-Ball Superradiance.

Clockwork cosmology (2023)
Journal Article
Wood, K., Saffin, P. M., & Avgoustidis, A. (2023). Clockwork cosmology. Journal of Cosmology and Astroparticle Physics, 2023(07), Article 062. https://doi.org/10.1088/1475-7516/2023/07/062

The higher order generalisation of the clockwork mechanism to gravitational interactions provides a means to generate an exponentially suppressed coupling to matter from a fundamental theory of multiple interacting gravitons, without introducing larg... Read More about Clockwork cosmology.

Optimisation of Thimble simulations and quantum dynamics of multiple fields in real time (2022)
Journal Article
Woodward, S., Saffin, P. M., Mou, Z. G., & Tranberg, A. (2022). Optimisation of Thimble simulations and quantum dynamics of multiple fields in real time. Journal of High Energy Physics, 2022(10), Article 82. https://doi.org/10.1007/JHEP10%282022%29082

We apply the Generalised Thimble approach to the computation of exact path integrals and correlators in real-time quantum field theory. We first investigate the details of the numerical implementation and ways of optimizing the algorithm. We subseque... Read More about Optimisation of Thimble simulations and quantum dynamics of multiple fields in real time.

Charge-swapping Q-balls in a logarithmic potential and Affleck-Dine condensate fragmentation (2022)
Journal Article
Hou, S. Y., Saffin, P. M., Xie, Q. X., & Zhou, S. Y. (2022). Charge-swapping Q-balls in a logarithmic potential and Affleck-Dine condensate fragmentation. Journal of High Energy Physics, 2022(7), Article 60. https://doi.org/10.1007/JHEP07%282022%29060

We study charge-swapping Q-balls, a kind of composite Q-ball where positive and negative charges co-exist and swap with time, in models with a logarithmic potential that arises naturally in supersymmetric extensions of the Standard Model. We show tha... Read More about Charge-swapping Q-balls in a logarithmic potential and Affleck-Dine condensate fragmentation.

Gravitational collapse of quantum fields and Choptuik scaling (2022)
Journal Article
Berczi, B., Saffin, P. M., & Zhou, S.-Y. (2022). Gravitational collapse of quantum fields and Choptuik scaling. Journal of High Energy Physics, 2022(2), Article 183. https://doi.org/10.1007/jhep02%282022%29183

Gravitational collapse into a black hole has been extensively studied with classical sources. We develop a new formalism to simulate quantum fields forming a black hole. By choosing a convenient coherent state, this formalism taps into well-establish... Read More about Gravitational collapse of quantum fields and Choptuik scaling.